Fluorinated alkyl carboxylate esters and fluorinated alkyl carboxylic copolymers obtained by copolymerization of fluorinated alkyl carboxylate esters with other monomer(s), which are capable of copolymerizing with the ester, have been used to impart water- and oil-repellency to fibers.
U.S. Pat. No. 3,239,557 discloses a process for preparing fluorinated alkyl carboxylate esters from fluorinated alkyl halides which comprises heating, under anhydrous conditions, the halides with alkali metal carboxylates in an unsubstituted monohydric aliphatic hydrocarbon alcohol as solvent, at a reaction temperature of from about 125 to about 200° C. for from about 1 to about 30 hours under autogenous pressure. This patent teaches to avoid preparing the ester by reacting the halide with a metal carboxylate using the corresponding acid as solvent, because extensive polymerization of both the acid solvent and ester products occurs for unsaturated acids. This patent also suggests reaction with a silver salt of a carboxylic acid is slow in comparison with an alkali metal carboxylate.
Winter et. al., in Chem. Mater., 1999, 11, 3044-3049, report that silver acrylate (made in situ from silver oxide and a slight molar excess of acrylic acid) reacts with SF5(CF2)2CH2CH2I in refluxing acetonitrile solvent for 27 hours to provide a 90:10 mixture of two olefins. Only a 20% yield of the acrylate ester, SF5(CF2)2CH2CH2OC(═O)CH═CH2 was obtained.
U.S. Pat. No. 6,660,803 discloses a method to prepare a polyfluoroalkyl (meth)acrylate ester by reacting a polyfluoroalkyl iodide with an alkali metal salt of (meth)acrylic acid in a solvent having a boiling point lower than that of the desired ester product (with alcohols, ketones, esters and nitriles cited as examples of solvents that can be used, preferably t-butanol) to obtain a reaction mixture containing a polyfluoroalkyl (meth)acrylate ester and a metal iodide. Specifically, this patent discloses reacting a polyfluoroalkyl iodide with an alkali metal salt of (meth)acrylic acid at a temperature of 150 to 220° C., for 1 to 5 hours (60 to 300 minutes). The fluoroalkyl(meth)acrylate product is susceptible to undesirable polymerization at such high temperatures.
The ester-forming reactions of alkyl iodides with sodium acrylate or potassium acrylate in the methods described above are invariably accompanied by dehydrohalogenation of the fluoroalkyl iodide to form, as a significant proportion of the low boiling point by-products, fluoroalkyl olefins (typically at least 10%), reducing the selectivity for the desired fluoroalkyl acrylate product as shown below:

There remains a need for a process to prepare a fluorinated alkyl carboxylate ester from a fluorinated alkyl iodide, which avoids dehydrohalogenation of the fluorinated alkyl iodide and polymerization of the product in the case of unsaturated esters. The present invention meets these needs.